Prefer iterator to vec

src/librustc/hir/lowering.rs

@@ -1459,10 +1459,9 @@ impl<'a> LoweringContext<'a> {
                             return n;
                         }
                         assert!(!def_id.is_local());
-                        let n = self.cstore
-                            .item_generics_cloned_untracked(def_id, self.sess)
-                            .lifetimes()
-                            .len();
+                        let item_generics =
+                            self.cstore.item_generics_cloned_untracked(def_id, self.sess);
+                        let n = item_generics.lifetimes().count();
                         self.type_def_lifetime_params.insert(def_id, n);
                         n
                     });

src/librustc/middle/resolve_lifetime.rs

@@ -1660,7 +1660,6 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     .or_insert_with(|| {
                         tcx.generics_of(def_id)
                             .types()
-                            .iter()
                             .map(|def| def.object_lifetime_default)
                             .collect()
                     })

src/librustc/traits/error_reporting.rs

@@ -378,7 +378,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             flags.push(("_Self".to_string(), Some(self.tcx.type_of(def.did).to_string())));
         }
 
-        for param in generics.types().iter() {
+        for param in generics.types() {
             let name = param.name.to_string();
             let ty = trait_ref.substs.type_for_def(param);
             let ty_str = ty.to_string();

src/librustc/traits/object_safety.rs

@@ -284,7 +284,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
 
         // We can't monomorphize things like `fn foo<A>(...)`.
-        if !self.generics_of(method.def_id).types().is_empty() {
+        if self.generics_of(method.def_id).types().count() != 0 {
             return Some(MethodViolationCode::Generic);
         }
 

src/librustc/traits/on_unimplemented.rs

@@ -243,7 +243,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
         let name = tcx.item_name(trait_def_id);
         let generics = tcx.generics_of(trait_def_id);
         let parser = Parser::new(&self.0);
-        let types = generics.types();
+        let mut types = generics.types();
         let mut result = Ok(());
         for token in parser {
             match token {
@@ -254,7 +254,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
                     // `{ThisTraitsName}` is allowed
                     Position::ArgumentNamed(s) if s == name => (),
                     // So is `{A}` if A is a type parameter
-                    Position::ArgumentNamed(s) => match types.iter().find(|t| {
+                    Position::ArgumentNamed(s) => match types.find(|t| {
                         t.name == s
                     }) {
                         Some(_) => (),
@@ -288,7 +288,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
         let name = tcx.item_name(trait_ref.def_id);
         let trait_str = tcx.item_path_str(trait_ref.def_id);
         let generics = tcx.generics_of(trait_ref.def_id);
-        let generic_map = generics.types().iter().map(|param| {
+        let generic_map = generics.types().map(|param| {
             (param.name.to_string(),
              trait_ref.substs.type_for_def(param).to_string())
         }).collect::<FxHashMap<String, String>>();

src/librustc/ty/mod.rs

@@ -803,28 +803,28 @@ impl<'a, 'gcx, 'tcx> Generics {
         self.parent_count + self.own_count()
     }
 
-    pub fn lifetimes(&self) -> Vec<&RegionParameterDef> {
+    pub fn lifetimes(&self) -> impl DoubleEndedIterator<Item = &RegionParameterDef> {
         self.params.iter().filter_map(|p| {
             if let GenericParam::Lifetime(lt) = p {
                 Some(lt)
             } else {
                 None
             }
-        }).collect()
+        })
     }
 
-    pub fn types(&self) -> Vec<&TypeParameterDef> {
+    pub fn types(&self) -> impl DoubleEndedIterator<Item = &TypeParameterDef> {
         self.params.iter().filter_map(|p| {
             if let GenericParam::Type(ty) = p {
                 Some(ty)
             } else {
                 None
             }
-        }).collect()
+        })
     }
 
     pub fn has_type_parameters(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
-        if self.types().len() != 0 {
+        if self.types().count() != 0 {
             return true;
         }
         if let Some(parent_def_id) = self.parent {
@@ -885,7 +885,7 @@ impl<'a, 'gcx, 'tcx> Generics {
             // And it can be seen that in both cases, to move from a substs
             // offset to a generics offset you just have to offset by the
             // number of regions.
-            let type_param_offset = self.lifetimes().len();
+            let type_param_offset = self.lifetimes().count();
 
             let has_self = self.has_self && self.parent.is_none();
             let is_separated_self = type_param_offset != 0 && idx == 0 && has_self;

src/librustc/ty/subst.rs

@@ -242,8 +242,7 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
     where FR: FnMut(&ty::RegionParameterDef, &[Kind<'tcx>]) -> ty::Region<'tcx>,
           FT: FnMut(&ty::TypeParameterDef, &[Kind<'tcx>]) -> Ty<'tcx> {
         // Handle Self first, before all regions.
-        let types = defs.types();
-        let mut types = types.iter();
+        let mut types = defs.types();
         let mut skip_self = defs.parent.is_none() && defs.has_self;
         if skip_self {
             let def = types.next().unwrap();

src/librustc/util/ppaux.rs

@@ -310,10 +310,10 @@ impl PrintContext {
             if let Some(def_id) = generics.parent {
                 // Methods.
                 assert!(is_value_path);
-                child_types = generics.types().len();
+                child_types = generics.types().count();
                 generics = tcx.generics_of(def_id);
-                num_regions = generics.lifetimes().len();
-                num_types = generics.types().len();
+                num_regions = generics.lifetimes().count();
+                num_types = generics.types().count();
 
                 if has_self {
                     print!(f, self, write("<"), print_display(substs.type_at(0)), write(" as "))?;
@@ -328,8 +328,8 @@ impl PrintContext {
                     assert_eq!(has_self, false);
                 } else {
                     // Types and traits.
-                    num_regions = generics.lifetimes().len();
-                    num_types = generics.types().len();
+                    num_regions = generics.lifetimes().count();
+                    num_types = generics.types().count();
                 }
             }
 
@@ -337,7 +337,7 @@ impl PrintContext {
                 if generics.types().last().map_or(false, |def| def.has_default) {
                     if let Some(substs) = tcx.lift(&substs) {
                         let tps = substs.types().rev().skip(child_types);
-                        for (def, actual) in generics.types().iter().rev().zip(tps) {
+                        for (def, actual) in generics.types().rev().zip(tps) {
                             if !def.has_default {
                                 break;
                             }

src/librustc_mir/monomorphize/collector.rs

@@ -1108,7 +1108,7 @@ fn create_mono_items_for_default_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                         continue;
                     }
 
-                    if !tcx.generics_of(method.def_id).types().is_empty() {
+                    if tcx.generics_of(method.def_id).types().count() != 0 {
                         continue;
                     }
 

src/librustc_mir/transform/check_unsafety.rs

@@ -357,7 +357,7 @@ fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: D
 
     // FIXME: when we make this a hard error, this should have its
     // own error code.
-    let message = if !tcx.generics_of(def_id).types().is_empty() {
+    let message = if tcx.generics_of(def_id).types().count() != 0 {
         format!("#[derive] can't be used on a #[repr(packed)] struct with \
                  type parameters (error E0133)")
     } else {

src/librustc_privacy/lib.rs

@@ -399,7 +399,7 @@ impl<'a, 'tcx> Visitor<'tcx> for EmbargoVisitor<'a, 'tcx> {
 
 impl<'b, 'a, 'tcx> ReachEverythingInTheInterfaceVisitor<'b, 'a, 'tcx> {
     fn generics(&mut self) -> &mut Self {
-        for def in &self.ev.tcx.generics_of(self.item_def_id).types() {
+        for def in self.ev.tcx.generics_of(self.item_def_id).types() {
             if def.has_default {
                 self.ev.tcx.type_of(def.def_id).visit_with(self);
             }
@@ -1335,7 +1335,7 @@ struct SearchInterfaceForPrivateItemsVisitor<'a, 'tcx: 'a> {
 
 impl<'a, 'tcx: 'a> SearchInterfaceForPrivateItemsVisitor<'a, 'tcx> {
     fn generics(&mut self) -> &mut Self {
-        for def in &self.tcx.generics_of(self.item_def_id).types() {
+        for def in self.tcx.generics_of(self.item_def_id).types() {
             if def.has_default {
                 self.tcx.type_of(def.def_id).visit_with(self);
             }

src/librustc_trans/debuginfo/mod.rs

@@ -417,7 +417,7 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
         let mut names = generics.parent.map_or(vec![], |def_id| {
             get_type_parameter_names(cx, cx.tcx.generics_of(def_id))
         });
-        names.extend(generics.types().iter().map(|param| param.name));
+        names.extend(generics.types().map(|param| param.name));
         names
     }
 

src/librustc_typeck/astconv.rs

@@ -209,7 +209,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         // whatever & would get replaced with).
         let decl_generics = tcx.generics_of(def_id);
         let num_types_provided = parameters.types.len();
-        let expected_num_region_params = decl_generics.lifetimes().len();
+        let expected_num_region_params = decl_generics.lifetimes().count();
         let supplied_num_region_params = parameters.lifetimes.len();
         if expected_num_region_params != supplied_num_region_params {
             report_lifetime_number_error(tcx, span,
@@ -221,9 +221,10 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         assert_eq!(decl_generics.has_self, self_ty.is_some());
 
         // Check the number of type parameters supplied by the user.
-        let ty_param_defs = &decl_generics.types()[self_ty.is_some() as usize..];
+        let ty_param_defs =
+            decl_generics.types().skip(self_ty.is_some() as usize).collect::<Vec<_>>();
         if !infer_types || num_types_provided > ty_param_defs.len() {
-            check_type_argument_count(tcx, span, num_types_provided, ty_param_defs);
+            check_type_argument_count(tcx, span, num_types_provided, &ty_param_defs);
         }
 
         let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
@@ -254,7 +255,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                 return ty;
             }
 
-            let i = i - self_ty.is_some() as usize - decl_generics.lifetimes().len();
+            let i = i - self_ty.is_some() as usize - decl_generics.lifetimes().count();
             if i < num_types_provided {
                 // A provided type parameter.
                 self.ast_ty_to_ty(&parameters.types[i])

src/librustc_typeck/check/compare_method.rs

@@ -377,7 +377,7 @@ fn check_region_bounds_on_impl_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     // but found 0" it's confusing, because it looks like there
     // are zero. Since I don't quite know how to phrase things at
     // the moment, give a kind of vague error message.
-    if trait_params.len() != impl_params.len() {
+    if trait_params.count() != impl_params.count() {
         let mut err = struct_span_err!(tcx.sess,
                                        span,
                                        E0195,
@@ -574,8 +574,8 @@ fn compare_number_of_generics<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                         -> Result<(), ErrorReported> {
     let impl_m_generics = tcx.generics_of(impl_m.def_id);
     let trait_m_generics = tcx.generics_of(trait_m.def_id);
-    let num_impl_m_type_params = impl_m_generics.types().len();
-    let num_trait_m_type_params = trait_m_generics.types().len();
+    let num_impl_m_type_params = impl_m_generics.types().count();
+    let num_trait_m_type_params = trait_m_generics.types().count();
     if num_impl_m_type_params != num_trait_m_type_params {
         let impl_m_node_id = tcx.hir.as_local_node_id(impl_m.def_id).unwrap();
         let impl_m_item = tcx.hir.expect_impl_item(impl_m_node_id);
@@ -728,7 +728,7 @@ fn compare_synthetic_generics<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let mut error_found = false;
     let impl_m_generics = tcx.generics_of(impl_m.def_id);
     let trait_m_generics = tcx.generics_of(trait_m.def_id);
-    for (impl_ty, trait_ty) in impl_m_generics.types().iter().zip(trait_m_generics.types().iter()) {
+    for (impl_ty, trait_ty) in impl_m_generics.types().zip(trait_m_generics.types()) {
         if impl_ty.synthetic != trait_ty.synthetic {
             let impl_node_id = tcx.hir.as_local_node_id(impl_ty.def_id).unwrap();
             let impl_span = tcx.hir.span(impl_node_id);

src/librustc_typeck/check/intrinsic.rs

@@ -45,7 +45,7 @@ fn equate_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         }
     }
 
-    let i_n_tps = tcx.generics_of(def_id).types().len();
+    let i_n_tps = tcx.generics_of(def_id).types().count();
     if i_n_tps != n_tps {
         let span = match it.node {
             hir::ForeignItemFn(_, _, ref generics) => generics.span,
@@ -346,7 +346,7 @@ pub fn check_platform_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     };
 
     let def_id = tcx.hir.local_def_id(it.id);
-    let i_n_tps = tcx.generics_of(def_id).types().len();
+    let i_n_tps = tcx.generics_of(def_id).types().count();
     let name = it.name.as_str();
 
     let (n_tps, inputs, output) = match &*name {

src/librustc_typeck/check/method/confirm.rs

@@ -332,7 +332,7 @@ impl<'a, 'gcx, 'tcx> ConfirmContext<'a, 'gcx, 'tcx> {
                 parent_substs.type_at(i)
             } else if let Some(ast_ty)
                 = provided.as_ref().and_then(|p| {
-                    p.types.get(i - parent_substs.len() - method_generics.lifetimes().len())
+                    p.types.get(i - parent_substs.len() - method_generics.lifetimes().count())
                 })
             {
                 self.to_ty(ast_ty)

src/librustc_typeck/check/mod.rs

@@ -1239,7 +1239,7 @@ pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item
         } else {
             for item in &m.items {
                 let generics = tcx.generics_of(tcx.hir.local_def_id(item.id));
-                if !generics.types().is_empty() {
+                if generics.types().count() != 0 {
                     let mut err = struct_span_err!(tcx.sess, item.span, E0044,
                         "foreign items may not have type parameters");
                     err.span_label(item.span, "can't have type parameters");
@@ -4799,7 +4799,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
             // Skip over the lifetimes in the same segment.
             if let Some((_, generics)) = segment {
-                i -= generics.lifetimes().len();
+                i -= generics.lifetimes().count();
             }
 
             if let Some(ast_ty) = types.get(i) {
@@ -4920,9 +4920,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // Check provided type parameters.
         let type_defs = segment.map_or(vec![], |(_, generics)| {
             if generics.parent.is_none() {
-                generics.types()[generics.has_self as usize..].to_vec()
+                generics.types().skip(generics.has_self as usize).collect()
             } else {
-                generics.types()
+                generics.types().collect()
             }
         });
         let required_len = type_defs.iter().take_while(|d| !d.has_default).count();
@@ -4957,7 +4957,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         }
 
         // Check provided lifetime parameters.
-        let lifetime_defs = segment.map_or(vec![], |(_, generics)| generics.lifetimes());
+        let lifetime_defs = segment.map_or(vec![], |(_, generics)| generics.lifetimes().collect());
         let required_len = lifetime_defs.len();
 
         // Prohibit explicit lifetime arguments if late bound lifetime parameters are present.
@@ -4968,7 +4968,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             let primary_msg = "cannot specify lifetime arguments explicitly \
                                if late bound lifetime parameters are present";
             let note_msg = "the late bound lifetime parameter is introduced here";
-            if !is_method_call && (lifetimes.len() > lifetime_defs.len() ||
+            if !is_method_call && (lifetimes.len() > required_len ||
                                    lifetimes.len() < required_len && !infer_lifetimes) {
                 let mut err = self.tcx.sess.struct_span_err(lifetimes[0].span, primary_msg);
                 err.span_note(span_late, note_msg);
@@ -4983,9 +4983,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             return;
         }
 
-        if lifetimes.len() > lifetime_defs.len() {
-            let span = lifetimes[lifetime_defs.len()].span;
-            let expected_text = count_lifetime_params(lifetime_defs.len());
+        if lifetimes.len() > required_len {
+            let span = lifetimes[required_len].span;
+            let expected_text = count_lifetime_params(required_len);
             let actual_text = count_lifetime_params(lifetimes.len());
             struct_span_err!(self.tcx.sess, span, E0088,
                              "too many lifetime parameters provided: \
@@ -4994,7 +4994,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 .span_label(span, format!("expected {}", expected_text))
                 .emit();
         } else if lifetimes.len() < required_len && !infer_lifetimes {
-            let expected_text = count_lifetime_params(lifetime_defs.len());
+            let expected_text = count_lifetime_params(required_len);
             let actual_text = count_lifetime_params(lifetimes.len());
             struct_span_err!(self.tcx.sess, span, E0090,
                              "too few lifetime parameters provided: \
@@ -5014,8 +5014,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         let segment = segment.map(|(path_segment, generics)| {
             let explicit = !path_segment.infer_types;
-            let impl_trait = generics.types().iter()
-                                             .any(|ty_param| {
+            let impl_trait = generics.types().any(|ty_param| {
                                                  match ty_param.synthetic {
                                                      Some(ImplTrait) => true,
                                                      _ => false,

src/librustc_typeck/check/wfcheck.rs

@@ -642,7 +642,6 @@ fn reject_shadowing_type_parameters(tcx: TyCtxt, def_id: DefId) {
     let generics = tcx.generics_of(def_id);
     let parent = tcx.generics_of(generics.parent.unwrap());
     let impl_params: FxHashMap<_, _> = parent.types()
-                                             .iter()
                                              .map(|tp| (tp.name, tp.def_id))
                                              .collect();
 

src/librustc_typeck/impl_wf_check.rs

@@ -105,7 +105,7 @@ fn enforce_impl_params_are_constrained<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         tcx, &impl_predicates.predicates.as_slice(), impl_trait_ref, &mut input_parameters);
 
     // Disallow ANY unconstrained type parameters.
-    for (ty_param, param) in impl_generics.types().iter().zip(impl_hir_generics.ty_params()) {
+    for (ty_param, param) in impl_generics.types().zip(impl_hir_generics.ty_params()) {
         let param_ty = ty::ParamTy::for_def(ty_param);
         if !input_parameters.contains(&ctp::Parameter::from(param_ty)) {
             report_unused_parameter(tcx, param.span, "type", &param_ty.to_string());
@@ -114,7 +114,7 @@ fn enforce_impl_params_are_constrained<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
     // Disallow unconstrained lifetimes, but only if they appear in assoc types.
     let lifetimes_in_associated_types: FxHashSet<_> = impl_item_refs.iter()
-        .map(|item_ref|  tcx.hir.local_def_id(item_ref.id.node_id))
+        .map(|item_ref| tcx.hir.local_def_id(item_ref.id.node_id))
         .filter(|&def_id| {
             let item = tcx.associated_item(def_id);
             item.kind == ty::AssociatedKind::Type && item.defaultness.has_value()
@@ -122,15 +122,11 @@ fn enforce_impl_params_are_constrained<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         .flat_map(|def_id| {
             ctp::parameters_for(&tcx.type_of(def_id), true)
         }).collect();
-    for (ty_lifetime, lifetime) in impl_generics.lifetimes().iter()
-        .zip(impl_hir_generics.lifetimes())
-    {
+    for (ty_lifetime, lifetime) in impl_generics.lifetimes().zip(impl_hir_generics.lifetimes()) {
         let param = ctp::Parameter::from(ty_lifetime.to_early_bound_region_data());
 
-        if
-            lifetimes_in_associated_types.contains(&param) && // (*)
-            !input_parameters.contains(&param)
-        {
+        if lifetimes_in_associated_types.contains(&param) && // (*)
+            !input_parameters.contains(&param) {
             report_unused_parameter(tcx, lifetime.lifetime.span,
                                     "lifetime", &lifetime.lifetime.name.name().to_string());
         }

src/librustdoc/clean/auto_trait.rs

@@ -226,7 +226,6 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
     fn generics_to_path_params(&self, generics: ty::Generics) -> hir::PathParameters {
         let lifetimes = HirVec::from_vec(
             generics.lifetimes()
-                    .iter()
                     .map(|p| {
                         let name = if p.name == "" {
                             hir::LifetimeName::Static

src/librustdoc/clean/mod.rs

@@ -1800,7 +1800,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics,
         // Bounds in the type_params and lifetimes fields are repeated in the
         // predicates field (see rustc_typeck::collect::ty_generics), so remove
         // them.
-        let stripped_typarams = gens.types().iter().filter_map(|tp| {
+        let stripped_typarams = gens.types().filter_map(|tp| {
             if tp.name == keywords::SelfType.name().as_str() {
                 assert_eq!(tp.index, 0);
                 None